Animation Nodes slow performance
The slow performance is most likely due to your unorganized and unoptimized node tree. In order to identify the source of the regression, we can measure the execution time of each of the individual nodes and identify the node(s) that takes the most time and try to refactor them. This measuring can be activates by pressing the details button here:



In your node tree, my best guess is, your Plane subprogram always generates the same mesh, yet you compute the mesh at every iteration! So simply move the node generating the plane outside of the loop and pass it as a parameter. Moreover, don't reinvent the wheel, use the Grid Mesh node instead. Also, remove all those viewer nodes, they have some impact on performance.